Vascular procedures to treat occlusive vascular diseases, such as angioplasty, atherectomy and stent placement, often cause blood clots to form and/or material to dislodge from inside the vessel walls and enter the bloodstream. The dislodged material (e.g., plaque), known as emboli, may be large enough to occlude smaller downstream vessels, potentially blocking blood flow to tissue. Additionally, the blood clots, known as thrombi, may be large enough or grow over time to form a blockage at the interventional site or at another downstream location should the thrombus become released into the bloodstream.
There are numerous previously known interventional systems and methods that employ a filter mechanism designed to capture material liberated from vessel walls during the treatment or diagnosis of vascular disease. Many of the more recent devices employ radially expandable filters disposed at the distal end of a guide wire. These filters have various configurations, such as mesh or microporous membranes in the form of sleeves, parachutes or baskets attached to the guide wire or other delivery mechanism by means of struts, wires, ribs or frames. The meshes are frequently made of woven or braided fibers or wires made of stainless steel, nitinol, platinum alloy, polyester, nylon or porous plastics, for example. The microporous membranes are typically made of a polymer material such as polypropylene, polyurethane, polyester, polyethylene tetraphlalate, polytetrafluoroethylene or combinations thereof.
Examples of procedures employing such filters include angioplasty, atherectomy, thrombectomy and stent placement. These procedures typically involve transluminally inserting and delivering within a vessel, a guide wire with an attached filter to a location distal to a lesion or treatment site, and deploying the filter. The interventional device is then delivered over the guide wire to the treatment site. During the treatment of a lesion within the patient's vessel, plaque is often liberated from the walls of the vessel creating emboli within the bloodstream. These emboli are then captured within the deployed filter, where they remain for the duration of the treatment procedure.
Depending on the amount of plaque dislodged from the vessel wall, the embolic filter may become occluded with emboli during an interventional procedure, thus preventing blood from flowing through the filter. As a result, a pool forms proximal to the filter. When the filter becomes full or occluded with emboli and debris, the interventional procedure may need to be terminated so that the filter can be removed from the vasculature. As such, the duration of the interventional procedure is dependent upon the emboli-filling capacity of the deployed filter.
Numerous approaches have been postulated to overcome the increased procedure times associated with the retrieval and subsequent exchange of emboli-laden filters from a patient's vasculature. For example, one such approach is to employ an aspiration device to aspirate emboli contained within a filter sac of a vascular filter, so as to eliminate the need to retrieve and exchange the filter when it becomes full of emboli. However, there are significant disadvantages associated with this approach, including increased procedural complexity, the need for additional components and the inability to completely aspirate emboli entrapped in the filter pores.
In view of the description of the foregoing devices and methods, it is desirable to provide an improved embolic filter system. Additionally, it is desirable to have such systems that provide for the rapid exchange of embolic filters during the course of an interventional diagnostic or therapeutic procedure and/or in which a stent is deployed. Further, it is advantageous to have such systems capable of delivering multiple filters and/or interventional devices without losing guide wire access to the target site. In addition, it is desirable that there be a safe withdrawal of the deployed embolic filters from the vasculature. It is also desirable to first insert a guide wire distal the target region, and then subsequently replace the guide wire with a filter wire attached to a filter. Insertion of a guide wire first, and then subsequently replacing the guide wire with a filter and filter wire, enables the clinician to more accurately maneuver the embolic filter across the site of the lesion.